A conventional catalytic converter using ammonia as an external reducing agent includes a reducing catalyst or a deNOx catalyst. Generally, NOx included in exhaust gases reacts with ammonia input from the outside and is then decomposed into nitrogen and water by a zeolite supporting a vanadium component, an iron component or a copper component, or a catalyst layer formed of a mixture including titanium oxide, vanadium oxide, tungsten oxide and/or molybdenum oxide.
FIG. 1 is a partially cut-away perspective view of a catalytic converter, and FIG. 2 is a sectional view of the catalytic converter, the interior of which is coated with SCR deNOx catalyst layers. The catalytic converter 10 is formed in an open-flow type honeycomb structure, in which a plurality of exhaust gas passages 11a and 11b, which are defined by porous partition walls 12, is provided between an inlet 15 and an outlet 16. DeNOx catalysts 30 are applied on the inner surfaces of the partition walls 12 to reduce, preferably, NO to N2. FIG. 4 is a partially cut-away perspective view of a filter type catalytic converter. FIG. 5 is a sectional view of a filter type catalytic converter, the interior of which is coated with SCR deNOx catalyst layers. The catalytic converter 100 includes a plurality of exhaust gas passages 11a and 11b which is defined by porous partition walls 120. Ends of inlets 150 and outlets 160 of the catalytic converter 100 are plugged in a staggered way (see reference numeral 130). DeNOx catalysts 300 are applied on the inner surfaces of partition walls 120 to reduce, preferably, NO to N2.
However, the above described catalytic converter requires the injection of ammonia thereinto from the outside, thus entailing problems related to the installation of the catalytic converter in a vehicle. The present inventors have researched catalytic converters in an attempt to overcome these problems, and, as a result, the present invention has been completed.